This invention relates to specialized industrial chambers such as freeze dryers, and more particularly to a novel sub-door assembly arranged to facilitate process control and automation.
The trend in many industries today is toward automation and quality control. As an example, the pharmaceutical industry is becoming more interested in automation and process control particularly from the standpoint of maintaining sterility and temperature control during manufacture and packaging of its products. Large freeze dryers, typical in the art, are utilized in the processing of drugs and the like, and U.S. Pat. No. 4,449,305 is illustrative of a conventional freeze dryer having a plurality of adjustable shelves and provided with means to automatially transfer items from the shelves of one series to the shelves of another series.
One of the first steps toward achieving automated chamber loading is to provide some access into the chamber for the loading of the shelves other than by utilizing the large main door. Ideally, the object is to expose only enough area required to load one shelf at a time. This ensures the least amount of exposure to the inside of the chamber. If, for example, the shelves inside the chamber were at a very low temperature, opening the main door could allow the shelves to warm up due to their exposure to the higher external temperature. Additionally, it permits a larger area for any contaminants to enter the chamber. Opening and closing the large main door each time a shelf is to be loaded is wasteful, time consuming, not cost effective and interferes with loading and other automation mechanisms.
Ideally, therefore, it is desirable to facilitate the automatic loading of a chamber while reducing the impact of the outside environment on the interior during such operation. Consequently, it is advantageous that a loading opening be configured to expose only enough area required to allow passage therethrough of material to be loaded onto each shelf one at a time. This allows systematic shelf loading, shelf by shelf, as each is sequentially raised to a prescribed receiving position at the opening. A sub-door would be arranged to automatically open and close the opening at appropriate times during the loading and unloading operation.
Although there is a demonstrated need for a sub-door assembly which is arranged to cooperate with automated and semi-automated loading systems such as has been described, none has heretofore been available.